Annulation (derived from annular, occasionally annelation) in organic chemistry is a chemical reaction in which a new ring is constructed on another molecule (often another ring).[1]
Examples are the Robinson annulation, Danheiser Annulation and certain cycloadditions. Annular molecules are constructed from side-on condensed cyclic segments, for example helicenes and acenes. In transannulation a bicyclic molecule is created by intramolecular carbon-carbon bond formation in a large monocyclic ring. An example is the samarium(II) iodide induced ketone - alkene cyclization of 5-methylenecyclooctanone which proceeds through a ketyl intermediate [2]:
Benzannulation
The term benzannulated compounds refers to derivatives of cyclic compounds (usually aromatic) which are fused to a benzene ring. Examples are listed in the table below:
| Benzannulated derivative | Source of cyclic compound |
|---|---|
| Benzopyrene | Pyrene |
| Quinoline | Pyridine |
| Isoquinoline | |
| Chromene | Pyran |
| Isochromene | |
| Indole | Pyrrole |
| Isoindole | |
| Benzofuran | Furan |
| Isobenzofuran | |
| Benzimidazole | Imidazole |
Transannular interaction
A transannular interaction in chemistry is any chemical interaction (favorable or nonfavorable) between different non-bonding molecular groups in a large ring or macrocycle [3]. See for an example the molecule atrane.
References
- ^ International Union of Pure and Applied Chemistry. "annulation". Compendium of Chemical Terminology Internet edition. International Union of Pure and Applied Chemistry. "annelation". Compendium of Chemical Terminology Internet edition.
- ^ Construction of Bicyclic Ring Systems via a Transannular SmI2-Mediated Ketone-Olefin Cyclization StrategyGary A. Molander, Barbara Czakó, and Michael Rheam J. Org. Chem.; 2007; 72(5) pp 1755 - 1764; (Article) doi:10.1021/jo062292d
- ^ Experimental evidence in support of transannular interactions in diketones Kata Mlinaric-Majerski, Marijana Vinkovic, Danko Škare, Alan P. Marchand Arkivoc DS-339E 2002 Online Article
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